The present invention relates to neurosurgical devices used for treating hydrocephalus and, more specifically, to ventriculoperitoneal (VP) shunts that relieve pressure on the brain caused by excess fluid accumulation within the brain.
Hydrocephalus is a condition caused by an abnormal accumulation of cerebrospinal fluid (CSF) within the ventricles of the brain. Cerebrospinal fluid is produced in the choroid plexuses of the ventricles of the brain and circulates through the ventricular system of the brain to the subarachnoid spaces in the cranium and spine to be absorbed into the bloodstream. The fluid is used to surround the brain and spinal cord and acts as a protective cushion or buffer against injury. It also contains nutrients and proteins for nourishment and functioning of the brain while clearing away waste products.
Hydrocephalus occurs when there is an imbalance between the amount of CSF that is produced and the amount that is absorbed. When CSF builds up within the brain, it causes the ventricles to enlarge and increases the pressure inside the skull.
Hydrocephalus is typically treated through the surgical placement of a shunt system within the brain. The shunt system places a drainage tube between the brain's ventricles or the subarachnoid space and another body region, typically the abdominal cavity (or pleural cavity, heart atrium, and others), where the CSF can be absorbed. This creates an alternative route for removal of CSF buildup within the brain. Valves may be positioned within the shunt pathway to regulate flow based upon differential pressure, i.e., the pressure difference at the proximal catheter tip and the pressure at the drainage end.
Shunt failure is a very common complication requiring immediate shunt revision (the replacement or reprogramming of the pre-existing shunt). A shunt malfunction that does not receive immediate medical attention can be life-threatening or result in permanent neurologic injury. The shunt failure rate is relatively high (in the pediatric population, the shunt failure rate after one year is 40-50% and after five years is at nearly 100%) and it is not uncommon for patients to have multiple shunt revisions within their lifetime.
A leading cause of shunt failure is partial or complete blockage of the shunt. Both the proximal catheter placed in the brain and the distal catheter that provides the draining may become blocked. Typically when there is a blockage, the shunt must be replaced.
Under-drainage due to shunt blockage can cause the ventricles to increase in size and fail to remedy the symptoms of hydrocephalus. However, over-drainage is also undesired since it decreases the size of the ventricles and creates slit like ventricles. Over-drainage has also been found to increase the likelihood of shunt blockages.